A liquid-crystal display device (LCD) is a display device in which transmission/blocking of light (ON/OFF of a display) is controlled by controlling an alignment of liquid crystal molecules exhibiting birefringence. A VA (Vertical Alignment) mode, an IPS (In-Plane Switching) mode, and so on may be used in the LCD as a display method. In the VA mode, liquid crystal molecules having negative dielectric constant anisotropy are aligned vertically relative to a substrate surface, and in the IPS mode, liquid crystal molecules having positive dielectric constant anisotropy are aligned horizontally relative to the substrate surface, and a transverse electric field is applied to a liquid crystal layer.
In the IPS mode, a transverse electric field is applied to the liquid crystal layer, and therefore features are applied to an electrode and a wiring. A typical IPS mode liquid-crystal display device includes a common electrode to which a reference potential is supplied and a pixel electrode to which a potential of a pixel to be displayed is supplied (see Patent Documents 1 to 4, for example). A scanning line to which a scanning signal is supplied, a thin film transistor (TFT), and so on are also provided. The common electrode and the pixel electrode both have a comb tooth shape and are disposed such that comb teeth of the respective electrodes are disposed alternately. The liquid crystal is driven by an electric field formed between the pixel electrode and the common electrode.
Patent Document 1: Japanese Patent Application Publication No. H10-301141
Patent Document 2: Japanese Patent Application Publication No. 2000-35590
Patent Document 3: Japanese Patent Application Publication No. 2003-295207
Patent Document 4: Japanese Patent Application Publication No. 2006-330215
In a liquid-crystal display device of a mode in which the electrode and the wiring are formed narrowly, the electrode and the wiring are preferably formed as narrowly as possible from the viewpoint of improving a transmittance. When the electrode and the wiring are formed too narrowly, however, a disconnection may occur, making it impossible to supply the required potential to the electrode and the wiring.
FIG. 73 is a planar schematic view showing a disconnection in a conventional liquid-crystal display device. Here, an IPS mode liquid-crystal display device will be described on the basis of Patent Document 1. Normally in an IPS mode liquid-crystal display device, various wirings and electrodes are provided on a TFT (thin film transistor) array substrate.
As shown in FIG. 73, the TFT substrate includes a scanning electrode wiring 125 and a first common electrode wiring 122. The scanning electrode wiring 125 and the first common electrode wiring 122 are formed on an identical plane. Further, an insulating film is formed on the scanning electrode wiring 125 and first common electrode wiring 122, and a signal electrode wiring 124, a pixel electrode wiring 121, and a second common electrode wiring 123 are formed on the insulating film. The first common electrode wiring 122 and the second common electrode wiring 123 are electrically connected. The scanning electrode wiring 125, signal electrode wiring 124, and pixel electrode wiring 121 are connected via a TFT 126 constituted by a semiconductor element. The TFT 126 functions as a switching element. The pixel electrode wiring 121 and the second common electrode wiring 123 respectively have a line width of 5 μm.
Opposed substrates having red, green, and blue color filters are disposed in positions opposing the TFT substrate via a liquid crystal layer. When the TFT 126 is ON, a signal potential is supplied to the pixel electrode wiring 121 from the signal electrode wiring 124. When the TFT 126 becomes unselected (OFF) thereafter, the potential of the pixel electrode wiring 121 is maintained such that an electric field is generated in a lateral direction between the pixel electrode wiring 121 and the second common electrode wiring 123. In accordance with an intensity of the electric field, an alignment direction of liquid crystal molecules aligned in a certain direction in a horizontal direction relative to the substrate surface changes to a different direction in-plane, and as a result, a polarization condition of light incident on the liquid crystal layer varies.
However, when a disconnection occurs in a location of the pixel electrode wiring 121 marked by an X symbol, as shown in FIG. 73, the signal potential is not supplied to the location that has become isolated due to the disconnection, and therefore an electric field is not generated between the isolated pixel electrode wiring 121 and the opposing second common electric wiring 123. Accordingly, a location indicated by diagonal lines in FIG. 73 no longer contributes to transmission, and as a result, a pixel in which the disconnection occurs is recognized as either a dark defect or a pixel having a drastically reduced brightness.